Mud gas sampling and logging system



May 7, 1968 J. M. HORETH ET AL 3,381,536

MUD GAS SAMPLING AND LOGGING SYSTEM 2 Sheets-Sheet 1 Filed Dec. 6, 1965ATTORNEY m 0 m w M 6 7 w. m 6 6 W c I NA E: H6O TNH A. ELDY H B P HM m Mum D M 9 m m M M 4 RTN 0 A H H W m M 0 w H C mm f N w (I T T C 6 R 4 m 7I. 5 m M F 6 G I M F r. H m AG E W H T L SW 3 B a U T H Dfi U U N MO M IMay 7, 1968 J. M. HORETH ET AL 3,381,536

MUD GAS SAMPLING AND LOGGING SYSTEM 2 Sheets-Sheet 2 Filed Dec. 6, 1965RICHARD H. LANGENHEIM, INVENTORS 8 WILLIAM Dv HOWARD BY jg? ATTORNEYUnited States Patent 3,381,536 MUD GAS SAMPLING AND LOGGING SYSTEM JohnM. Horeth, William 1). Howard, and Richard H.

Langenheim, Houston, Tex, assignors to Esso Production Research Company,a corporation of Delaware Continuation-impart of application Ser. No.294,674, July 12, 1263. This application Dec. 6, 1965, Ser.. No. 511,930

laims. (Cl. 73-4215) ABSTRACT OF THE DISCLOSURE A mud gas sampling andlogging system having sampling unit, a retort, and a gas collectingunit. The sampling unit is connected to the mud stream and adapted toperiodically obtain hermetically sealed mud samples. The samples areconducted in a hermetically sealed condition to the retort. The effluentof the retort is conducted into the gas collecting chamber from whichthe uncondensed gas is displaced by introduced fluids. A float valve isprovided in the collecting chamber to prevent entry of the condensedsteam and heavy hydrocarbons into the uncondensed-gas discharge ports.

This application is a continuation-impart of Ser. No. 294,674, filedJuly 12, 1963, now US, Patent No. 3,240,- 068, issued Mar. 15, 1966.

This invention relates to the drilling of boreholes in the earth, andmore particularly, to the logging of a rotary drilling operation by theperiodic sampling and analysis of the drilling mud to determine itslight hydrocarbon content.

It is a common practice in the drilling of oil and gas wells to sampleand analyze drilling fiuid returns from bottomhole to determine thenature of the strata being traversed by the drill. In this manner,direct evidence is obtained indicative of the presence or absence of oiland gas in the formations being penetrated. The presence of hydrocarbongases and other light hydrocarbons in the drilling mud returns, even inamounts of only a few parts per million, is frequently the first andmost reliable indication of the likelihood that a commerciallyproductive well can be completed. This amount of hydrocarbons entrained,dissolved, or occluded in the mud stream, is much too small to bedetermined by simple analytical means. It requires instead highlyspecialized equipment and techniques.

Recent advances in gas chromatography have led to the development ofcommercially available devices which provide an accurate and dependableanalysis of light hydrocarbons, subject primarily to the requirementthat the sample supplied to the chromatograph be substantially free ofcontamination, including particularly water and heavier hydrocarbons. Ithas thus become desirable that field procedures for sampling the returnmud stream be further developed and improved for the purpose ofeliminating errors which are usually inherent in manual operations,including primarily the loss of hydrocarbon gases from the mud returnstream due to exposure of the mud to the atmosphere.

In addition to sampling errors, a further problem is to eliminate errorscaused by an incomplete and/or inconsistent separation of the lighthydrocarbons from the mud samples. It is also essential to provide asample for chromatograph analysis which is free of contamination fromwater and heavier hydrocarbons.

Accordingly, it is an object of the present invention to provide a fullyautomated system for mud-gas sampling and analysis. It is a specificobject of the invention 3,381,536 Patented May 7, 1968 to provideapparatus for sampling and degassing drilling mud in a reliable andquantitative manner suitable for field operation. It is a further objectof the invention to provide a gas collection device which is suitablefor receiving gases and vapors from the degassing zone, and which iscapable of separating the hydrocarbon gases from heavier hydrocarbonvapors and. water vapor.

These and other objects of the invention will be apparent from thefollowing detailed description of a preferred embodiment of theinvention.

FIGURE 1 is a schematic diagram indicating the relationship of the majorsubcombinations to the complete system of the invention.

FIGURE 2 is an elevation of the sampling unit of the invention, showingits relationship to the degassing chamher or retort.

FIGURE 3 is a vertical cross-section of the sampling unit, showing itsessential features.

FIGURE 4 is an elevational view, partly in section, showing the gascollection unit.

FIGURE 5 is a vertical cross-section of the gas collection unit, showingthe detailed structure of certain valves and ports associated therewith.

FIGURE 6 is a horizontal cross-section of the gas collection chambertaken along the line 66 of FIG- URE 4.

FIGURE 7 is a horizontal cross-section of the gas collection chambertaken along the line 77 of FIGURE 4.

In FIGURE 1, the mud returned stream to be analyzed is supplied tosampling unit 11 by means of mud inlet line 12. While sampling unit 11is on standby, the mud is bypassed through outlet line 13. Periodically,the mud stream is passed through the sampling chamber from which aportion of the mud is injected through line 14 into retort 15. Retort 15is operated at a temperature within the range of 200450 F., andpreferably in the range of 300-400 F., for the purpose of quantitativelyexpelling hydrocarbon gases contained in the drilling mud sample,including primarily methane, ethane and propane, along with steam vaporand the vapors of butane, pentane, and heavier hydrocarbons, if present.

At the end of about 1 to 3 minutes heating, the retort is vented throughline 16 to gas collection chamber 17. In chamber 17 the hydrocarbongases, including butane and pentane, if desired, are separated from theheavier hydrocarbon vapors and steam vapor, whereupon the uncontaminatedgas sample is expelled through line 18 for analysis by recordingchromatograph 19.

In FIGURES 2 and 3, the detailed construction of the sampling unit isshown. The mud return stream enters the unit through line 12, and duringthe standby cycle is bypassed through line 21 into discharge line 13.During the bypass period, push rod 22 is displaced from its indicatedposition by means of double-acting pneumatic piston 23, such that port24 is closed by valve 25, and such that port 26 is opened by valve 27. Acontinuous flow is thus maintained through lines 12, 21, and 13, wherebyfresh return mud is available for sampling at the desired timeintervals.

When sampling, push rod 22 is returned to the position indicated inFIGURE 3, whereby port 26 is closed and port 24 is opened. Mud thenflows through line 28 and chamber 29, then through lines 30 and 31, andis discharged through line 13. Mud is allowed to flow through chamber 29for a sufiicient time to insure complete displacement of any mudremaining from a previous sampling cycle, and to insure complete fillingof chamber 29 with fresh mud. Port 24 is then closed by valve 25,whereby port 26 is again opened, permitting mud to bypass through line21. Port 32 is left open for a short time which permits any air whichmay have been trapped in chamber 29 to bleed through line 30. Push rod34 is then displaced from its indicated position by means ofdouble-acting pneumatic piston 35 whereby port 32 is closed by valve 33,thereby closing chamber 29 which is now completely liquid-full. A checkvalve (not shown) is provided in line 14 to further insure a completeseal of chamber 29.

Injection ram 36 is then forced into chamber 2% by means ofdouble-acting pneumatic piston 37. As the ram enters chamber 29, avolume of mud is forced through line 14 into retort 15, the displacedvolume being exactly equal to the fractional volume of chamber 29occupied by ram 36. At the end of its stroke, the ram is seated againstport 38, thereby forming a seal between chamber 29 and retort 15.

After a suitable period of heating in retort 15, the gases and vaporsexpelled from the mud sample are vented from the retort through line 16,into gas collection chamber 17. Upon venting the retort, a substantialvolume of steam is generated, in addition to that released earlier. Theadditional steam sweeps out the hydrocarbon gas sample, insuring itscomplete removal from the retort. Retort is then flushed with waterintroduced through line 39 and discharged through line 40. Water mayalso be introduced through line 14 to provide additional flush- Asillustrated in FIGURE 3, push rods 22 and 34 appear to occupy a largefraction of the total inside diameter of lines 28 and 30, respectively.Actually, however, the push rods should have a somewhat smallerdiameter, in order to provide increased clearance for the flow ofdrilling fluid, particularly when handling a fluid which carriesentrained cuttings of larger than average size.

Referring to FIGURES 4 and 5, gas collection chamber 17 is filled with aliquid, for example water, supplied through line 41 in preparation forreceiving the gas sample through line 16. As chamber 17 is filled withwater, float 42 is displaced upward until it contacts stop 43, whichprojects into the chamber a sufiicient distance to prevent float 42 fromblocking either of ports 44 and 45. Then, as the sample gases enterchamber 17 through line 16, water is displaced through line 41, with theformation of a gas pocket at the upper end of the chamber. As the waterlevel falls, float 42 is lowered until it reaches the end of line 16which serves as a stop. During entry of the sample through line 16,valves 46 and 437 are held in the closed position by push rods 48 and49, which are actuated by double-acting pneumatic pistons 50 and 51,respectively. From the total mixture of gases and vapors which enterthrough line 16, the steam and heavy hydrocarbon vapors are condensed.

The collected sample is then displaced from chamber 17 by the opening ofvalve 47 and the introduction of water through line 41. Referring toFIGUURE 7, a mechanism is shown whereby the introduction of waterthrough line 41 is interrupted in time to prevent the entry ofcontaminants into line 13. Light source 52 and photocell 53 are providedon opposite sides of chamber 17, near the upper end thereof, such thatlight from source 52 must pass through chamber 17 in order to activatecell 53. Thus, as water enters line 41 displacing the gas sample throughline 18, float 42 is raised to a position which blocks the passage oflight through chamber 17, thereby deactivating cell 53, which generatesa signal used to energize piston 51, closing valve 47. Before analysisby chromatograph 19, the sample passing through line 18 must be dilutedto a constant, predetermined volume in order that the sequence ofanalytical results may be consistently related one to the other. Thissample dilution is accomplished in the chromatograph sample loop inaccordance with the conventional operation of commercially availablechromatographs. A suitable gas chromatograph for use in accordance withthe present invention is the Chronofrac model VP-I of Fisher ScientificCompany, as fully described in their Bulletin No. 619.

Thereafter, in preparation for receiving the next successive sample,chamber 17 is purged by the opening of valve 46 and the injection ofwater through line 54. The waste is then discharged through line 41.Subsequently, a new supply of water is introduced through line 41 aspreviously described.

The complete system of the invention is readily automated, similarly asshown in the disclosure of US. 294,- 674, filed July 12, 1963, of whichthe present application is a continuation-in-part. That is, the sequenceof operations described above may be programmed by a series of rotarycams which are timed to engage a series of microswitches, in thesequence necessary to actuate valves which control the flow of the mudstream, and to actuate the remaining valves or relays which similarlycontrol the remaining stages of the operation.

What is claimed is:

1. Apparatus for sampling and degassing a drilling fluid stream whichcomprises a hermetically scalable sampling chamber, a retort incombination with said sampling chamber, means for periodically flowingsaid fluid through said sampling chamber means for temporarilyhermetically sealing said sampling chamber, hermetically scalable meansfor conducting fluid from said sampling chamber to said retort, andmeans for displacing a predetermined volume of fluid from said samplingchamber and for hermetically sealing said conducting means from saidsampling chamber.

2. Apparatus as defined by claim 1 wherein said sampling chamber has aninlet port and first and second outlet ports, wherein said means fortemporarily sealing said sampling chamber includes means for closingsaid inlet port and said first outlet port of said sampling chamber, andwherein said means for conducting fluid into said retort includesconduit means connecting said second outlet port of said samplingchamber with said retort.

3. Apparatus as defined by claim 2 wherein said means for displacing thefluid from said sampling chamber cornprises an injection ram extendingthrough a wall of said sampling chamber at a point opposite said secondoutlet port therein, a portion of said injection ram being adapted toseal against said second outlet port, and means for forcing said raminto said chamber and against said second outlet port.

4. Apparatus as defined by claim 1 further comprising gas collectionmeans connected to receive a gas sample periodically expelled from saidretort, said gas collection means comprising an elongated, substantiallyvertically disposed vessel, means for admitting a gas and vapor streamfrom said retort to the interior volume of said vessel, means forcondensing steam and heavy hydrocarbon vapors from said total sample,means for displacing the remaining uncondensed gases from said vessel,outlet means in said vessel for discharging said displaced gases, andmeans for preventing discharge of the condensed steam and heavyhydrocarbons from said outlet means.

5, Apparatus as defined by claim 4 wherein said means for condensingsteam and heavy hydrocarbon vapors comprises means for providing a bodyof cooling fluid within said vessel, in direct contact with the streamof gases and vapors entering said vessel.

6. Apparatus as defined by claim 5 wherein said means for displacing theuncondensed gases comprises means for introducing additional coolingliquid into said vessel.

7. Apparatus as defined in claim 4 wherein said means for preventingdischarge of condensed steam and condensed heavy hydrocarbons comprisesfloat means within said vessel at the gas-liquid interface, a lightsource, and a photoelectric cell, said source and cell being located onopposite sides of said gas collection vessel at a. level near the upperend thereof, whereby the approach of said gasliquid interface to theupper end of said chamber causes the float to intercept the path of liht between said source and said cell.

6 8. Apparatus as defined in claim 7, further comprising 10. A device asdefined by claim 9, further comprising means operative upon theinterception of said light path means for periodically flushing saidvessel to remove confor inte ru tin the dis lacement of fluids from saidtaminantsr p g P References Cited vessel.

9. A gas collection device comprising an elongated ves- 5 UNITED S ATESP TENTS sel having upper, lower, and intermediate ports therein,1,837,858 12/1931 Grace 73-422 float means in said vessel, means forrestricting move- 5 955 Bliss et a1. 73421.5 X ment of said float meansbetween the upper and inter- FOREIGN PATENTS mediate ports of saidvessel, a photoelectric cell and a 10 600 450 4/1948 Great Britain.light source in combination with said vessel, said cell and source beingarranged to detect the arrival of said float DAVID SCHONBERG, P'YmaryExaminermeans at a point near said upper port. S. CLEMENT SWISHER,Examiner.

